PROGRESS OF MICROSCOPICAL SCIENCE. 105 



possess the granular characteristic ; there are no spindle-shaped fibres 

 of connective tissues about them ; they behave very differently under 

 the micro-chemical tests applied to the other variety of spots. The 

 points of resemblance are mainly in colour and apparent density. 

 Neither of them have any investing membrane. 



V. A fifth variety, as large in size as the third, possesses a dense 

 investing membrane, which resists carmine staining and is less gra- 

 nular than the third and fourth. It exists in the same brain with the 

 fourth variety. These spots or masses of the fifth variety are called 

 " colloid," because of their resemblance to such growth, and are found 

 in the medulla oblongata and pons Varolii. The last three varieties 

 of degenerated masses, or spots, have one featui'e in common — a well- 

 defined edge, a clean-cut margin, easily made out. 



VI. A sixth variety, common in cases of dementia, and w^here the 

 atheromatous capillary is found, is one in which the mass j)asses in- 

 sensibly into the surrounding normal tissues. This form is larger 

 and less distinct than the others. It more nearly resembles normal 

 brain tissites. Sometimes these masses are lobulated. They are 

 granular and dense, less numerous than in the other varieties, and do 

 not ajjpear in clusters. They appear to destroy or transform the 

 tissues, and if surrounding a capillary, destroy its walls. A jwint 

 of resemblance in common with the third variety is, that connective- 

 tissue fibre appears in both. 



The condition of the cellular structures of the brain, of the nerve 

 fibres and so-called lymjjh spaces, are all fields rich in results not 

 here spoken of. 



Tlie Development of Bone. — Perhaps the first authority on this 

 subject at the present moment is M. Eanvier, who lately read a paper 

 on it before the French Academy of Sciences. This paper forms the 

 subject of the follomng note, which is communicated by Mr. E. Klein 

 to the ' Medical and Surgical Recorder ' for July 15th. To study the 

 growth and development of bone tissue, Ranvier uses the bones of the 

 embryo, which are placed in absolute alcohol for twenty-four hours, 

 having previously been freed of the surrounding soft parts (excei^t the 

 periosteum). After that, they are transferred to a saturated solution of 

 picric acid, in which fluid they are kept imtil they become soft enough 

 to be fit for sections. In order to make thin and successful sections, 

 the softened bone is plunged into a thick solution of giun-arabic for 

 forty-eight hours, and then into alcohol of forty degrees. Now it is 

 easy to obtain very uniform sections through all parts of the bone, i.e. 

 bone matrix, medulla, and periosteum. The sections having been 

 washed in distilled water for twenty-four hours or more, in order to 

 dissolve the gum, they are stained with picro-carminate of ammonia, 

 and finally mounted in glycerine. In a longitudinal section through 

 a long bone of an embryo of a mammalian animal, passing from the 

 periosteum towards the axis, it is easy to see a well-marked boundary 

 between the periosteal bone and the cartilaginous bone. The latter 

 occupies the centre, and has an hour-glass shape in the longitudinal 

 section, whereas the periosteal bone forms on each side a semilunar 

 mass. The long bone at this stage of development may be correctly 



